1. Field of the Invention
The present invention relates to the field of photography and, more particularly, to photographic apparatus for exposing and processing "self-developing" film units.
2. Description of the Prior Art
The current state of the art in "one-step photographic systems" features integral or "nonpeel-apart film units" and highly automated cameras for exposing and processing these film units.
In a typical system, the film units are held in a film container which also includes a battery for powering electrical systems of the camers. Once the film container is loaded in the camera, the user frames the subject to be photographed, focuses the optical system, and presses a button to initiate a cycle of camera operation.
If the camera is of the single lens reflex type, the operating cycle consists of converting the optical system from the viewing mode to an exposure mode; exposing the forwardmost film unit in the film container; advancing the exposed film unit from the container to a processing station where a compressive pressure is applied to distribute a fluid processing composition within the film unit, thereby initiating a development and diffusion transfer processes; ejecting the processed film unit, at least partially, from the camera; and resetting the camera mechanisms for the next cycle of camera operation. The complete cycle of operation may occur in as little as 1.5 seconds.
In nonreflex cameras, the step of converting the optical system from the viewing and focusing mode to the exposure mode, and the subsequent reset of this subsystem, is, of course, unnecessary.
The present invention relates to camera mechanisms and/or systems for initiating, controlling, and/or performing the sequence of camera functions outlined above.
For the purposes of this disclosure, the term sequence of sequencing means the orderly occurrence of the above functions. It does not means some of the functions cannot occur at the same time or overlap. For example, it is a common practice to have at least some of the film exposure reset functions going on during the film advance, processing, and film eject portions of the operating cycle.
The prior art is replete with camera mechanism and/or systems for initiating, controlling or performing one or more or all of the above functions. Of special interest are those systems which include a sequencing or timing wheel, gear, or cam that is driven through a single 360.degree. revolution during the course of a camera operating cycle and initiates, controls and/or performs functions in a dependent relationship with respect to the angular disposition of such a rotating member relative to a predetermined starting position.
The term timing wheel found in many prior art disclosures is not a very accurate description, because in many systems, the rotating wheel does not operate on a linear-time base. For example, its rotation may stop one or more times during the course of the camera cycle of operation or the initiation of rotation may not coincide with the beginning of the cycle. Therefore, it will be understood that when the term sequencing wheel or gear is used in this disclosure, it may be interchanged with the term timing wheel or gear in other prior art disclosures.
The following are representative examples of cameras, disclosed in the prior art, that feature a single revolution sequencing member for initiating, controlling or performing one or more of the above-described functions.
U.S. Pat. No. 3,683,771 issued to E. H. Land on Aug. 15, 1972 discloses a camera having a single revolution cam for advancing a film unit from the exposure position to the processing station. U.S. Pat. No. 3,714,879, issued to E. H. Land, et al. on Feb. 6, 1973 describes a highly automated camera which has a single revolution timing gear for positioning a reflex member and coordinating a plurality of electrical switching functions. U.S. Pat. No. 3,744,388, issued to I. Erlichman on July 10, 1973 shows a reflex camera which includes a single revolution member for positioning a reflex mirror and advancing a film unit. U.S. Pat. No. 3,757,657, issued to V. K. Eloranta, et al. discloses a single revolution crank which performs the functions of advancing a film unit from the exposure position to a pair of rollers, driving the processing rollers, and recocking the shutter. U.S. Pat. No. 3,826,655, issued to R. J. Borel et al. on July 30, 1974 describes a self-developing camera which includes a single revolution timing gear for operating an electrical switch and a film advance mechanism.
The highly automated self-developing cameras that are presently on the market are relatively expensive because of complicated mechanism needed to perform so many interrelated functions during a very short (1.5 second) camera cycle. Also, the manufacturing costs are inflated because these cameras are very compact and require miniaturized components which must be made and assembled to extremely tight manufacturing tolerances that generally are not found in cameras that are aimed toward the mass-amateur-camera market.